Studies with Model Membranes: Part XIX - Evaluation of Permselectivity & Thermodynamically Effective Fixed Charge Density of Mercuric Tungstate Parchment Supported Membrane

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Studies with Model Membranes: Part XIX - Evaluation of Permselectivity & Thermodynamically Effective Fixed Charge Density of Mercuric Tungstate Parchment Supported Membrane

7-1

Studies with model membranes

The transport processes occuring across the parchment supported membrane have been extensively studied by using Nernst Planck flux equation taking into account the membrane resistance Rm. membrane potential Em. etc. The diffusion rate sequence and selectivity of the membrane for various uni, bi and trivaient cations were found to be dependent on the difference in the hydration energies of counter ions in the external solution. The various activation thermodynamic parameters namely enthalpy of activation ΔH≠, free energy of activation ΔF≠ and entropy of activation ΔS≠ were evaluated by applying the theory of Absolute Heaction Mate. The values of AS≠ were found to be negative indicating that diffusion lakes place with partial immobilization in the membrane phase. Λ formal relation between ΔHhydration,.ΔFhydration, and ΔShydration with corresponding values of ΔH≠, AP≠ and AS≠ for diffusion was also found to exist for the membrane. The effective fixed charge density and permselectivity were also evaluated by the method of irreversible thermodynamics of polystyrene moulded membranes which point towards the weak field strength of the charged groups thereby confirming our results for dilfusion studies

Studies with Polystyrene Based Zinc &' Ferric Phosphate Membranes: Evaluation of Effective Fixed Charge Density & Test of Recent Theory of Membrane Potential Based on' Non-equilibrium Thermodynamics

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Studies with model membranes

The thermodynamically effective fixed charge density of polystyrene moulded membranes have been determined by the most recent method of Nagasawa et al. The theoretical equations based on non equilibrium thermodynamics for membrane potential and bi-ionic potential derived by Toyoshima and Nozaki have also been applied and tested with polystyrene moulded membranes. It was found that the theoretically calculated bi-ionic potentials agree well with the experimentally observed values